The goal of this study is to evaluate the differences in functional physiopathology of the opioid and noradrenergic systems between Parkinson's patients with central pain and Parkinson's patients without central pain. Using PET-MRI data, investigators aim to observe opioids receptors availability using [11C]Carfentanil (µ opioid receptor agonist) and altered α2-AR density with [11C]Yohimbine (adrenergic α2 receptor antagonist).

Inclusion Criteria:

• Diagnosis of Parkinson's disease based on MDS-UPDRS criteria (Group 1 and 2)
• Dopaminergic therapy stable with stable dose for at least 4 weeks prior to J0
• Affiliate to a social security or similar system
• Having given written consent to participate in the study, free and informed.
• Having chronic pain more than 3 month (Group 1)
• Without chronic pain (Groupe 2 and 3)
• Having central pain using specific algorithm (Marques et al., 2019)
• Having pain intensity at least 4 on VAS (Visual Analogue Scale) during the last month (Group 1)
• Having pain intensity lower than 3 on VAS (Visual Analogue Scale) during the last month (Group 2 and 3)

Exclusion Criteria:

• Having atypical Parkinson's disease (Group 1 and 2)
• Parkinson's disease with disabling dyskinesia and/or severe tremor (Group 1 and 2)
• Any contraindications to having a brain MRI or PET scan (e.g., pacemaker, metal foreign body, claustrophobia, deep brain stimulation or apomorphin pump unable to be turn off)
• History of head trauma with loss of consciousness lasting more than 30 minutes
• Not agreeing to be informed in the event of incidental discovery of an abnormality on MRI or during neuropsychological assessment
• Presence of cognitive dysfunction (defined as MoCA score < 24)
• Severe depression (BDI > 29)
• unable to stop the opioid treatment the week before the imaging exam ( e.g., Antarène codéine, Claradol codéine, Codoliprane, Dafalgan codéine, Euphon, Klipal, Lindilane, Néo-codion, Paderyl, Prontalgine, Pulmoserum, Tussipax ; Opium : Izalgi, Lamaline, Colchimax, Dropizal ; Morphine : Actiskenan, Moscontin, Oramorph, Sevredol, Skenan ; Buprénorphine : Bupensan, Buvidal, Orobupre, Sixmo, Suboxone, Subutex, Temgesic, Zubsolv ; Dihydrocodéine : Dicodin ; Hydromorphone : Sophidone ; Nalbuphine : Nalpain ; Fentanyl : Abstral, Actiq, Breakyl, Durogesic, Effentora, Instanyl, Matrifen, Pecfent, Recivit ; Méthadone : Methadone AP-HP, Zorvon ; Oxycodone : Oxsynia, Oxycontin, Oxynorm, Oxynormoro ; Tramadol : Biodalgic, Contramal, Ixprim, Monoalgic, Monocrixo, Orozamudol, Skudexum, Topalgic, Zaldiar, Zamudol, Zumalgic)
• unable to stop any treatment
• Treated with level 1 analgesics (NSAIDs, acetaminophen) or coanalgesics (antidepressants, antiepileptics) unless treatment has been stable for at least 4 weeks prior to the study and does not interfere with the noradrenergic system (list above).
• Presenting or having presented a dependence on any addictive substance according to DSM-IV-TR criteria, with the exception of tobacco.
• Having used recreational drugs interfering with the opioid and noradrenergic systems (cannabis, CBD, opiates, MDMA, ecstasy) in the last 3 months or chronic use
• Pregnant women, women in labor or nursing mothers
• Persons deprived of their liberty by judicial or administrative decision
• Under psychiatric care
• Admitted to a health or social institution for purposes other than research
• Under legal protection (guardianship, curatorship)
• Participant in another interventional study with an exclusion period still in progress at pre-inclusion
• Having exceeded the annual amount of compensation authorized for participation in research protocols

It is not definied yet